Pump and manufacturing method thereof

ABSTRACT

A pump includes a pump unit having an impeller for sucking and/or discharging liquid; a motor unit for driving the pump unit; a case for accommodating the pump unit; a partition plate for isolating the motor unit from the pump unit; and a mold resin integrally formed with the motor unit to protect the motor unit. Further, a bottom portion of a cylindrical portion projecting from the partition plate to the motor unit has a liquid-free surface having a convex spherical shape. Moreover, a method of manufacturing a pump, the method includes the steps of installing a partition plate at a lower half; installing a stator and a controlling part at the partition plate; closing the lower half with an upper half; curing resin after filling the resin into a cavity formed between the lower and the upper half; opening a mold; and extracting a molded motor product.

FIELD OF THE INVENTION

The present invention relates to a pump driven by a motor for sucking and discharging liquid, and a manufacturing method thereof.

BACKGROUND OF THE INVENTION

In general, a pump includes a motor unit having a stator for generating a magnetic field and a controller for controlling the stator, a pump unit having an impeller driven by the magnetic field generated from the stator and sucking/discharging liquid such as liquid etc., and a partition plate for isolating the motor unit from the pump unit.

Particularly, in order to prevent corrosion of the motor unit due to intrusion of liquid leaked from the pump unit or high humidity in pump installation environment, resin is applied to the motor unit for protection.

In the above described pump, since the partition plate can be deformed toward the outside of the pump due to a pressure generated during operation of the pump, a bottom surface of the partition plate should have a large thickness. In addition, use of a large amount of resin may cause increase in manufacturing cost of the pump (see, for example, Japanese Patent Laid-open Publication No. 2004-60620).

Further, when resin is injected into an injection mold in order to cover the motor unit with the resin and cure the resin, the bottom surface of the partition plate is pressed and deformed by a resin pressure. It is, therefore, difficult to obtain an inner dimension of the pump unit within a desired tolerance limit. For this reason, parts related to position precision, for example, an impeller, etc. disposed in the pump should be machined by a lathe and so on, thereby increasing the manufacturing cost of the pump.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide a pump capable of reducing a material used for a partition plate, and suppressing deformation of a bottom surface of the partition plate to increase a dimension stability of product.

In accordance with an embodiment of the present invention, there is provided a pump including a pump unit having an impeller for sucking/discharging liquid, a motor unit for driving the pump unit, a case for accommodating the pump unit, a partition plate for isolating the motor unit from the pump unit, and a mold resin integrally formed with the motor unit to protect the motor unit, wherein a bottom portion of a cylindrical portion projecting from the partition plate to the motor unit has a liquid-free surface having a convex spherical shape surface.

Here, the bottom portion of the cylindrical portion has a relatively small area of plate and a high strength.

As a result, it is possible to reduce a material used for the partition plate. In addition, it is possible to provide the pump capable of suppressing deformation of the bottom surface of the partition plate to increase dimension stability of products.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention will become apparent from the following description of an embodiment given in conjunction with the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of a pump in accordance with a first embodiment of the present invention;

FIG. 2 is a cross-sectional view showing a process of installing parts at a lower half in accordance with the embodiment of the present invention;

FIG. 3 is a cross-sectional view showing a process of closing a mold before forming a molding process in accordance with the embodiment of the present invention;

FIG. 4 is a cross-sectional view showing a process of filling resin into a mold in accordance with the embodiment of the present invention; and

FIG. 5 is a cross-sectional view showing a process of extracting a motor product after the molding process in accordance with the embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENT

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings so that they can be readily implemented by those skilled in the art.

Embodiment 1

As shown in FIG. 1, a mold resin 2 formed of heat curable plastic, etc. is installed at a left side of a pump unit 4 to cover a motor unit 1 for driving the pump unit 4. A case 3 formed of plastic such as PPS (polyphenylene sulfide) or a metal such as a stainless steel is disposed at a right side of the pump unit 4.

A partition plate 5 formed of plastic such as PPS or a metal such as a stainless steel is similarly installed between the motor unit 1 and the case 3 isolating the motor unit 1 from the pump unit 4 to prevent intrusion of circulation liquid into the motor unit 1 from the pump unit 4. In addition, the partition plate 5 projects at its center adjacent to the motor unit 1 in a cylindrical shape. That is, the partition plate 5 has a cylindrical portion 5A having a size sufficient to accommodate the pump unit 4 therein. A flange in contact with the case 3 and the motor unit 1 is formed around an opening of the cylindrical portion 5A.

The motor unit 1 includes a magnetic field generating stator 6 having a hollow cylindrical shape, a controller 6 for controlling the stator 6, and a mold resin 2 cured to cover the stator 6 and the controller 7. The stator 6 is disposed on a periphery of the cylindrical portion 5A of the partition plate 5, and the outside of the stator 6 is covered with the resin.

A support plate 8 is connected to a left side of the stator 6, and a controller 7 having electronic parts 16A and 16B, such as resistors, transistors, and the like, is attached to the support plate 8.

Meanwhile, the pump unit 4 includes a cylindrical rotor 11 formed of a permanent magnet and rotated by the magnetic field generated from the stator 6; a cylindrical impeller 13 integrally formed with the rotor 11 and formed of plastic such as PPS to suck/discharge circulation liquid by using a plurality of blades 12 attached to its surface; a cylindrical shaft 14 formed of a metal such as stainless steel and rotatably supporting the rotor 11 and the impeller 13; and hollow cylindrical reception plates 15 formed of ceramic for fixing the shaft 14.

The rotor 11 is disposed while facing the stator 6 with the partition plate 5 interposed therebetween in the cylindrical portion 5A protruded toward the motor unit 1.

The impeller 13 having the plurality of blades 12 formed at its outer surface is disposed at a right side of the rotor 11 and integrally formed therewith, and the shaft 14 for rotatably supporting the rotor 11 and the impeller 13 is installed at the center of the rotor 11 and the impeller 13.

In addition, the reception plates 15 are attached to both ends of the shaft 14 to fix the shaft 14.

When the pump as described above is driven, a pressure in the pump unit 4 is increased. Therefore, the increased inner pressure may be applied to a liquid contact surface 5 a inside the bottom portion 5B of the cylindrical portion 5A of the partition plate 5, thereby causing deformation of the partition plate 5 toward the mold resin 2. However, since a liquid-free convex surface 5 b of the bottom portion 5B at the cylindrical portion 5A of the partition plate 5 has a spherical shape, for example, a radius of about 300 mm, the convex surface 5 b has a second moment of area larger than that of a conventional flat surface having a uniform thickness to increase its strength, though the convex surface has a relatively small cross-section, thereby suppressing deformation of the bottom surface of the partition plate. As a result, it is possible to reduce an amount of material used for the partition plate 5, thus reducing the manufacturing cost thereof.

In addition, when the liquid contact surface 5 a of the bottom surface of the partition plate is flat, the bottom portion has a variable thickness, for example, an outer periphery of about 2 mm and a center of about 3 mm. Therefore, a second moment of area of the variable thickness becomes about 2.5 times larger than that of the uniform thickness of 2 mm, thereby increasing the strength. Alternatively, when the liquid contact surface 5 a of the bottom surface of the partition plate is concave, whereas the bottom portion has a uniform thickness, e.g., a hollow spherical shape of about 2 mm thickness, a second moment of area of the concave shape becomes approximately 1.25 times larger than that of the uniform thickness of 2 mm, thereby increasing the strength.

Here, a process of covering the motor unit 1 with mold resin will be described.

As shown in FIG. 2, reference numeral 9 designates a lower half of a forming mold. The lower half 9 has a cylindrical convex portion 20 corresponding to the cylindrical portion 5A of the partition plate 5. First, the partition plate 5 is installed at the lower half 9, and then, the stator 6 and the controller 7 are installed at the cylindrical portion 5A projected from the partition plate 5. At this time, the controller 7 has already been attached to the support plate 8 provided at the stator 6.

In FIG. 2, reference numeral 10 designates an upper half of the forming mold. When the forming apparatus is initiated, as shown in FIG. 3, the lower half 9, the stator 6 and the controller 7 are raised toward the upper half 10, and the mold gets closed thereafter. When the mold is closed, a cavity 21 is formed in the mold. Then, resin is introduced from a resin inlet port 17 formed at the upper half 10, and a pressure is continuously applied to the resin from the forming apparatus, thereby spreading the mold resin 2 to all the corners in the mold cavity 21. In FIG. 4, the mold resin 2 is shown as being dispersed to all the corners in the cavity 11.

Here, a pressure is applied to the liquid-free surface 5 b of the bottom surface of the partition plate from the forming apparatus via the resin. A gap S of about 0.2 mm may be generated between the liquid contact surface 5 a of the bottom surface of the partition plate 5 and a ceiling surface 20 a of the convex portion 20 of the lower half 9 due to a dimension difference of the partition plate 5. When the strength of the bottom surface of the partition plate (the bottom portion 5B of the cylindrical upper part 5A) is insufficient, the bottom surface may be deformed by the resin pressure applied to the liquid-free surface 5B of the bottom surface of the partition plate 5 until the liquid contact surface 5 a of the bottom surface of the partition plate facing the liquid-free surface makes contact with a surface of the upper surface 12 a of the lower half 9.

As a result, a position of the reception plate installation surface 18 may be deformed toward the lower half 9 such that the position dimension of the reception plate installation surface 18 may be undesirably different from the original layout (design) when the components are completed. However, since the liquid-free surface 5 b has a convex spherical shape while the surface can resist the resin pressure based on the theory that surface particles push each other to a pressure applied to the mold resin 2 by the forming apparatus, it is possible to suppress deformation of the bottom surface of the partition plate 5 to increase dimension stability of products.

In the following processes, after keeping the mold closed until the mold resin 2 is cured, the mold is opened and the molded motor product is extracted. FIG. 5 illustrates the molded motor product extracted from the mold. Reference numeral 19 designates a spool, which may be detached using a tool such as a nipper to complete the molded motor product.

While a liquid supply apparatus adapting a pump in accordance with a first embodiment of the present invention has been described as a bath liquid circulation apparatus, the pump in accordance with the present invention may be adapted to various other liquid supply apparatuses such as a well pump apparatus, a hot liquid supply apparatus, a drain liquid supply apparatus, and so on.

The pump unit in accordance with the present invention may be adapted to various pumps used for a fuel cell device, a heat pump apparatus, and so on.

While the invention has been shown and described with respect to the embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims. 

1. A pump comprising: a pump unit having an impeller for sucking and/or discharging liquid; a motor unit for driving the pump unit; a case for accommodating the pump unit; a partition plate for isolating the motor unit from the pump unit; and a mold resin integrally formed with the motor unit to protect the motor unit, wherein a bottom portion of a cylindrical portion projecting from the partition plate to the motor unit has a liquid-free surface having a convex spherical shape.
 2. The pump of claim 1, wherein a liquid contact surface of the bottom portion of the cylindrical portion has a concave spherical shape.
 3. A method of manufacturing a pump, the method comprising the steps of: installing a partition plate at a lower half; installing a stator and a controlling part at the partition plate; closing the lower half with an upper half; curing resin after filling the resin into a cavity formed between the lower and the upper half; opening a mold; and extracting a molded motor product. 